Fixture facilitating heat sink fabrication

ABSTRACT

A fixture to facilitate fabrication of a heat sink includes a base plate to support a lower section of the heat sink, and multiple registration pins extending from the base plate. A platen is provided over a heat transfer element (HTE) of the heat sink, with the platen including slip fit regions to slip fit around respective registration pins, and with the lower section and HTE disposed between the base plate and the platen, and forming a fixture stack segment aligned with an active region of the cold plate. A load plate is provided which includes slip fit regions configured to slip fit around corresponding registration pins with the load plate disposed over the fixture stack segment. The load plate includes a single load pin centrally disposed to apply a load to the fixture stack segment and facilitate bonding the lower section and HTE together.

BACKGROUND

The power dissipation of integrated circuit chips, and the modulescontaining the chips, continues to increase in order to achievecontinuing increases in processor performance. This trend poses acooling challenge at both the module and system levels. With everincreasing heat dissipation from electronic devices, and continuingreduction in overall form factor, thermal management remains animportant element in electronic product design. Performance reliabilityand life expectancy of electronic components, such as integrated circuitchips, are inversely related to the component operating temperature.

Heat sinks function by dissipating thermal energy or heat generated by acomponent, such as an electronic component, into a cooler ambient, forinstance, air passing across the heat sink, and transfer thermal energyfrom the component at a higher temperature to the air at a lowertemperature, which typically has a significantly greater heat capacity.

In one design of a heat sink, a metal plate having a flat surface may beprovided with an array of comb or fin-like protrusions to increase theheat sink's surface area contacting an airflow as the air passes acrossthe heat sink, which increases the heat dissipation rate. A high thermalconductivity of the heat sink combined with a large surface areaprovided by such fin-like structures may result in rapid transfer ofthermal energy to surrounding, cooler air.

More aggressive liquid-cooled heat sinks (or cold plates) may berequired to actively cool certain high-heat generating electroniccomponents, such as integrated circuit chips. In a liquid-cooled coldplate implementation, a coolant, such as water, is provided to flowthrough the cold plate and extract heat conducted to the cold plate fromone or more heat-generating electronic components.

SUMMARY

In one or more aspects, a fixture is provided herein to facilitatefabrication of a cold plate with multiple heat transfer elements. Thefixture includes a base plate to support a lower section of the coldplate, with the cold plate including multiple active regions. Eachactive region is to include a respective heat transfer element tofacilitate cooling a respective heat generating electronic component.The fixture further includes multiple registration pins extending fromthe base plate, and multiple platens to reside over an upper section ofthe cold plate. A platen of the multiple platens includes slip fitregions configured to slip fit around respective registration pins ofthe multiple registration pins with the lower section and the uppersection of the cold plate disposed between the base plate and theplaten, and forming a fixture stack segment aligned with the heattransfer element in a respective active region of the multiple activeregions of the cold plate. The fixture further includes multiple loadplates. A load plate of the multiple load plates includes slip fitregions configured to slip fit around corresponding registration pins ofthe multiple registration pins with the load plate disposed over thefixture stack segment, above the platen of the multiple platens, and theload plate including a single load pin. The single load pin in the loadplate is centrally disposed in the load plate to facilitate applying aload to the fixture stack segment to facilitating bonding the lowersection, the respective heat transfer element and the upper section ofthe cold plate together.

In another aspect, a method of facilitating fabrication of a cold platewith multiple heat transfer elements is provided. The method includesassembling a fixture, including providing a base plate to support alower section of the cold plate, the cold plate including multipleactive regions, each active region including a respective heat transferelement to facilitate cooling a respective heat-generating electroniccomponent; and positioning multiple registration pins to extend from thebase plate. Further, assembling the fixture includes slip fittingmultiple platens to reside above an upper section of the cold plate, aplaten of the multiple platens including slip fit regions configured toslip fit around respective registration pins of the multipleregistration pins, with the lower section and the upper section of thecold plate disposed between the base plate and the platen, and forming afixture stack segment aligned with a heat transfer element in arespective active region of the multiple active regions of the coldplate. Further, the method includes slip fitting multiple load plates,where a load plate of the multiple load plates includes slip fit regionsconfigured to slip fit around corresponding registration pins of themultiple registration pins, with the load plate disposed over thefixture stack segment, above the platen of the multiple platens, and theload plate including a single load pin. The single load pin of the loadplate is centrally disposed in the load plate to facilitate applying aload to the fixture stack segment to facilitate bonding the lowersection, the respective heat transfer element and the upper section ofthe cold plate together.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more aspects of the present invention are particularly pointedout and distinctly claimed as examples in the claims at the conclusionof the specification. The foregoing and other objects, features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a cross-sectional elevational view of one embodiment of a heatsink (configured as a flexible cold plate) coupled to an electronicassembly with three heat generating electronic components to be cooled,the heat sink or flexible cold plate being configured with enhancedflexibility, and to be fabricated in accordance with one or more aspectsof the present invention;

FIG. 2A depicts an assembled view of one embodiment of a flexible coldplate such as depicted in FIG. 1, with multiple active regions, and thatis to be fabricated in accordance with one or more aspects of thepresent invention;

FIG. 2B is a cross-sectional plan view of one embodiment of the flexiblecold plate of FIG. 2A, taken along line 2B-2B thereof, that is to befabricated in accordance with one or more aspects of the presentinvention;

FIG. 3 is an exploded view of one embodiment of a flexible cold platesuch as depicted in FIGS. 1-2B to be fabricated using a fixture andfabrication process, in accordance with one or more aspects of thepresent invention;

FIG. 4A depicts one embodiment of an assembled flexible cold platewithin a fixture to facilitate bonding the flexible cold plate together,in accordance with one or more aspects of the present invention;

FIG. 4B is an exploded view of the fixture of FIG. 4A, in accordancewith one or more aspects of the present invention;

FIG. 5 illustrates a partially assembled fixture such as depicted inFIGS. 4A & 4B, with the platens being shown slip fit in position aroundrespective registration pins over corresponding active regions of thecold plate, and forming respective fixture stack segments, in accordancewith one or more aspects of the present invention;

FIG. 6 depicts the fixture and flexible cold plate assembly of FIG. 5with the load plates shown being slip fit in position over respectivefixture stack segments of the assembly, in accordance with one or moreaspects of the present invention;

FIG. 7 depicts the fixture and cold plate assembly of FIGS. 4A-6 withthe load pins shown being torqued to apply a load force ‘F’ to theplatens, and thereby to the cold plate in the respective active regionsof the cold plate, in accordance with one or more aspects of the presentinvention; and

FIGS. 8A & 8B depict one embodiment of a process for fabricating aflexible cold plate using a fixture such as depicted in FIGS. 4A-7, inaccordance with one or more aspects of the present invention.

DETAILED DESCRIPTION

Aspects of the present invention and certain features, advantages anddetails thereof, are explained more fully below with reference to thenon-limiting example(s) illustrated in the accompanying drawings.Descriptions of well-known systems, devices, processing techniques,etc., are omitted so as to not unnecessarily obscure the invention indetail. It should be understood, however, that the detailed descriptionin this specific example(s), while indicating aspects of the invention,is given by way of illustration only, and not by way of limitation.Various substitutions, modifications, additions, and/or arrangements,within the spirit and/or scope of the underlying inventive concepts willbe apparent to those skilled in the art from this disclosure. Notefurther that numerous inventive aspects and features are disclosedherein, and unless inconsistent, each disclosed aspect or feature iscombinable with any other disclosed aspect or feature as desired for aparticular application, for instance, to facilitate fabricating aparticular heat sink, such as a flexible cold plate with multiple activeregions.

As noted, this disclosure relates to fixtures and fabrication processesfor fabricating heat sinks used for cooling electronic components, andin particular, to fixtures for fabricating flexible thin-walled coldplates. Before discussing the fixtures and fabrication processes indetail, an exemplary flexible cold plate and cooled electronic assemblyare described below with reference to FIGS. 1-3.

FIG. 1 depicts one embodiment of a cooled electronic assembly 100, whichincludes, in the depicted embodiment, a liquid-cooled cold plate 110 andan electronic assembly 120 that together form cooled electronic assembly100. By way of example only, electronic assembly 120 includes threeheat-generating electronic components 125 to be actively cooled vialiquid-cooled cold plate 110. Liquid-cooled cold plate 110correspondingly includes three active regions 112 (i.e., thermallyfunctional regions dissipating heat), each positioned, sized andconfigured to couple to (and overlay) a respective heat-generatingelectronic component 125 of electronic assembly 120. The active regions112 of liquid-cooled cold plate 110 are physically coupled toheat-generating electronic components 125 via respective thermalinterface material (TIM) 126 contacts. The thermal interface material126 is selected to facilitate conduction of heat from theheat-generating electronic components 125 to the respective activeregion 112 of liquid-cooled cold plate 110 when in operation.

In the implementation depicted, each active region 112 includes a heattransfer element 114, which may have any of a variety of configurationsto facilitate transfer of heat conducted from the respectiveheat-generating electronic component 125 to coolant (not shown) flowingthrough liquid-cooled cold plate 110. For instance, heat transferelement 114 in each active region may be a finsink structure comprisinga plurality of coolant flow channels through which liquid coolant flowsfrom, for instance, an inlet plenum 111 to an outlet plenum 113 ofliquid-cooled cold plate 110 when operational. Note also that a varietyof liquid coolants may be used within liquid-cooled cold plate 110, withwater or an aqueous-based solution being two examples only.

Liquid-cooled cold plate 110 and heat transfer elements 114 may befabricated of any of a variety of thermally conductive materials. In oneembodiment, liquid-cooled cold plate 110 includes lower and upperthin-walled sheets or plate members, referred to herein as lower andupper sections or shells, which are bonded together along a periphery.In one or more implementations, the thin-walled sheets may be formed ofa metal heat sink material, such as copper, aluminum, zinc, stainlesssteel, etc., and have a thickness ranging from, for instance, 0.5 mm to1.5 mm, and that is suitable for cooling an electronic component, suchas an integrated circuit chip, graphics processor chip, etc., or that isconfigured to cool an electronic assembly or module. Additionally, heattransfer elements 114 may be formed of a same or different metal heatsink material than the shells, such as copper, aluminum, zinc, stainlesssteel, etc., and have any desired size and configuration.

In one or more embodiments, liquid-cooled cold plate 110 formed as a‘flexible’ cold plate by incorporating lateral compliance into avertically flexible or compliant cold plate, which allows strain to beabsorbed by the cold plate rather than by, for instance, thermalinterface material (TIM) 126 providing the interface between theheat-generating electronic components 125 and the corresponding activeregions 112 of liquid-cooled cold plate 110. In FIG. 1, the verticallyflexible, or compliant, cold plate is shown secured in heat exchangerelation with the heat-generating electronic components 125 mounted on asubstrate 121 of electronic assembly 120. As shown, heat transferelements 114 are mounted within liquid-cooled cold plate 110 between thelower and upper sections or shells. In one or more implementations, theheat transfer elements 114 may include fins, pins or other heat transferstructures and may be metallurgically joined, such as brazed or welded,for instance, to the lower section of the liquid-cooled cold plate, aswell as to the upper section of the liquid-cooled cold plate.

The thin-walled upper and lower sections or shells of liquid-cooled coldplate 110 provide flexibility to accommodate, for instance, differentlevel electronic components (e.g., chips) within electronic assembly120. Lateral compliance features such as bends may also be added toallow for lateral expansion and contraction of liquid-cooled cold plate110 relative to the substrate, without moving or significantly stressingthe individual thermal interface material 126 regions or contactsbetween heat-generating electronic components 125 and active regions 112of liquid-cooled cold plate 110. In one or more implementations,liquid-cooled cold plate 110 may provide lateral compliance featuresthat minimize or eliminate sheer stress and sheer strain developed inthe horizontal direction at the interface between the cold plate and thethermal interface material 126 by allowing for horizontal expansion andcontraction of the liquid-cooled cold plate 110 relative to theunderlying electronic assembly 120 without moving or otherwise stressingthe individual thermal interface material regions in the horizontaldirection.

In the embodiment of FIG. 1, stiffness of the cold plate wall may befurther reduced by providing reduced height wall sections between activeregions 112 of liquid-cooled cold plate 110. More particularly, asdepicted in the example of FIG. 1, the height of the cold plate in theactive regions 112 may be greater than the height of the cold plate inthe intermediate regions 116, between active regions 112. The greaterheight in the active regions 112 facilitates accommodating the heattransfer elements 114, such as the noted finsinks, in the active regions112, while the reduced height in the intermediate regions 116 enhancesflexibility of the cold plate.

FIG. 2A illustrates liquid-cooled cold plate 110 of FIG. 1, with araised coolant inlet coupling 210 and a raised coolant outlet coupling212 extending from the upper section of liquid-cooled cold plate 110. Inoperation, a coolant loop (not shown) may be coupled to liquid-cooledcold plate 110 via a coolant supply line (not shown) being coupled influid communication with raised coolant inlet coupling 210 and a coolantreturn line (not shown) being coupled in fluid communication with raisedcoolant outlet coupling 212, which together to facilitate flow of liquidcoolant through liquid-cooled cold plate 110.

FIG. 2B depicts a cross-sectional plan view of one embodiment of theflexible liquid-cooled cold plate 110 of FIG. 2A, taken along line 2B-2Bthereof. In this embodiment, the heat transfer elements 114 in activeregions 112 are depicted as finsinks (by way of example only), whichinclude cooling fins. If desired, the finsinks and/or cooling fins mayhave different lengths in the different active regions 112. Moregenerally, heat transfer elements 114, may have any desired position,configuration, and/or size to facilitate cooling of a respectiveheat-generating electronic component of an electronic assembly to whichthe cold plate is to operatively attach for removal of heat. Forinstance, if one of the electronic components produces a greater amountof heat or is physically larger, then the active region 112 over thatparticular electronic component may be differently configured (e.g., belarger) than the active regions over the other electronic components towhich the cold plate is coupled.

As depicted in FIG. 2B, intermediate regions 116 of reduced height inthe example of FIG. 2A may also have a reduced width, which furtherfacilitates flexibility of the liquid-cooled cold plate 110 whenpositioned in place over the electronic assembly with the multipleheat-generating electronic components to be cooled, such as shown inFIG. 1. Note also that the exemplary embodiment of FIGS. 1-2B, withthree electronic components to be cooled and three active regions in thecold plate, is provided by way of example only. Any number of activeregions, including one, two, three, or more, may be defined within aflexible, liquid-cooled cold plate (to be fabricated as describedherein), to cool any number of electronic components of an electronicassembly.

FIG. 3 depicts an exploded view of one embodiment of liquid-cooled coldplate 110, such as depicted in FIGS. 1-2B. In FIG. 3, liquid-cooled coldplate 110 is shown unassembled and includes, in one or moreimplementations, a lower section or shell 300 and an upper section orshell 301 to be bonded together using, for instance, a braze or soldermaterial 302 along the periphery, where lower section 300 and uppersection 301 physically contact. Further, in this embodiment, a firstjoining material 310, such as a first braze or solder material, may beprovided between the respective heat transfer element 114 and lowersection 300 of liquid-cooled cold plate 110, and a second joiningmaterial, such as a second braze or solder material 320 may be providedabove heat transfer elements 114 to physically attach each heat transferelement 114 to upper section 301 of liquid-cooled cold plate 110.Additionally, raised coolant inlet coupling 210 and raised coolantoutlet coupling 212 may be metallurgically joined to upper section 301of liquid-cooled cold plate 110 using, for instance, second joiningmaterial 320. In one or more implementations, the raised coolant inletand outlet couplings 210, 212 are joined at respective openings in uppersection 301 to allow for coolant to flow through the liquid-cooled coldplate via the couplings. By way of example, the first joining material310 and the second joining material 320 may be different joiningmaterials, such as different braze or solder materials, or may be thesame joining materials. In one or more embodiments, first joiningmaterial 310 may be a sheet of braze or solder material placed inbetween a respective heat transfer element 114 and lower section 300 ofliquid-cooled cold plate 110 prior to heat treatment of the cold plateto metallurgically bond the thermally conductive components together.

In operation, the first joining material 310 will be of greatersignificance in terms of the performance of liquid-cooled cold plate 110than the second joining material 320, since the first joining materialis in the thermal conduction path from the respective heat-generatingelectronic component (see FIG. 1) when the liquid-cooled cold plate 110is operatively positioned above and in contact with the electronicassembly. In order to provide good thermal conduction across a braze orsolder interface between heat transfer element 114 and lower section 300of liquid-cooled cold plate 110, the percent of brazing or solderingvoids between the heat transfer element and the lower section needs tobe minimized, or even eliminated. This issue can be significant since iftoo great a void area exists at the bond, or interface, then efficiencyof the cold plate is reduced, and since there is no feasible rework ofsuch a liquid-cooled cold plate once fabricated, the cold plate wouldneed to be discarded.

In one or more embodiments, since the liquid-cooled cold plate 110 ofFIGS. 1-3 is of a flexible design, such as described herein, brazing theindividual active regions 112 to achieve uniformity between themetallurgical interfaces coupling the heat transfer elements 114 and thelower section 300 in the respective active regions may be a significantissue, which is advantageously addressed using a fixture and fabricationprocess such as disclosed herein below with reference to FIGS. 4A-8B.

FIG. 4A depicts one embodiment of a fixture and cold plate assembly,generally denoted 400, in accordance with one or more aspects of thepresent invention. As depicted, the fixture and cold plate portions ofassembly 400 are ready to run through a furnace for heat treatment tometallurgically join the sections, and the couplings to the uppersection, and heat transfer elements to the lower section of theflexible, liquid-cooled cold plate 110. FIG. 4B depicts an exploded viewof the fixture and cold plate assembly 400 of FIG. 4A, illustratingcomponents of the fixture 401 (FIG. 4A), in accordance with one or moreaspects of the present invention.

As shown in FIG. 4B, in one or more implementations, the assembly mayinclude a registration plate 410 with alignment features, such asopenings 411 and alignment pins 412 to facilitate placement of a baseplate 415 of the fixture onto registration plate 410, as well asalignment of registration pins 420 relative to registration plate 410.In one embodiment, registration pins 420, which are static loadregistration pins, may be bolts that are threadedly secured in positionrelative to registration plate 410 and base plate 415 using mating nuts421. Further, the static load registration pins include respectiveregistration pin heads 422.

Carbon blocks 430, 431 may be used above and below liquid-cooled coldplate 110, for instance, above and below the active regions of the coldplate to provide anti-stick surfaces above and below the active regionsof the liquid-cooled cold plate 110. By way of example only, the fixturecomponents, such as base plate 415 and platens 440 (discussed below),may be made of stainless steel, while the outer liquid-cooled cold platesections could be, for instance, copper. Also, note that although shownassembled in FIG. 4B, liquid-cooled cold plate 110 may be assembled (inone or more embodiments) within the fixture in a manner such asdescribed above in connection with FIG. 3, and below with reference toFIGS. 8A & 8B. For instance, joining materials may be disposedinternally between the respective components of the liquid-cooled coldplate. The joining materials, such as the first and second joiningmaterials at the lower and upper surfaces of the heat transfer elementswithin the active regions may be provided as, for instance, sheets ofmaterial (such as sheets of braze or solder material). Additionally,joining material may be provided along the periphery where the lower andupper sections of the liquid-cooled cold plate contact, as well asbeneath the raised couplings which are to be joined to the upper sectionof the liquid-cooled cold plate at the respective coolant inlet andoutlet openings formed in the upper section.

As further shown in FIG. 4B, the fixture includes multiple platens 440which, in the embodiment depicted, are identically configured to have afirst slip fit region 441 (e.g., opening, recess, etc.) and a secondslip fit region 442 (e.g., opening, recess, etc.) positioned and sizedto facilitate slip fitting the platen around a respective pair ofregistration pins 420 as the fixture is being assembled. The fixturealso includes multiple load plates 450 which, in the embodimentdepicted, are also identically configured, and a first slip fit region451 and a second slip fit region 452 sized and shaped to facilitate slipfitting each load plate around its corresponding registration pins,which may be the same or different registration pins from the respectiveplaten. In the embodiment depicted, a load plate 450 slip fits aroundthe same registration pins as a respective platen 440. Each load plateincludes a single load pin 455, which is a dynamic load pin that iscentrally disposed in the load plate 450 to facilitate applying auniform load to the respective platen 440, or more generally, to therespective fixture stack segment including the underlying platen 440 anda respective active region of cold plate 110.

The raised coolant inlet coupling 210 and coolant outlet coupling 212have pre-formed joining material disposed between the couplings and theupper section of liquid-cooled cold plate 110 and, in one or moreembodiments, carbon circles or rings 461 may be placed on top of theraised inlet and outlet couplings 210, 212, with the carbon circles 461being configured to mate with an alignment outrigger 460, for instance,with respective bores in the alignment outrigger 460. Alignmentoutrigger is configured to hold the raised inlet and outlet couplings210, 212, in position during heat treatment of the assembly tofacilitate fabricating the liquid-cooled cold plate.

By way of further example, FIGS. 5-7 illustrate assembly of the fixtureabout the cold plate at different stages. In FIG. 5, the fixture isshown with the liquid-cooled cold plate 110 positioned as describedabove relative to the base plate, and including carbon blocks above andbelow the active regions of the liquid-cooled cold plate. In FIG. 5, theplatens 440 are shown being slip fit into place about their respectiveregistration pins 420. In particular, the first slip fit regions 441 inplatens 440 are slip fit into the corresponding registration pin on oneside of the base plate, and the second slip fit regions 442 in platens440 are slid in a rotating manner to slip fit about the correspondingregistration pins 420 on the other side of the base plate. As notedabove, in one or more implementations, each platen may have an identicalconfiguration (as one example only). The platens 440 include a furtheropening or recess 444 which is positioned to allow the end positionedplatens to wrap around the corresponding raised coolant inlet or coolantoutlet coupling when the platen is positioned adjacent to the coupling.

In FIG. 6, load plates 450 are shown being slip fit in place aroundtheir corresponding registration pins 420 above respective fixture stacksegments 500 and overlying a respective platen 440. In the embodimentillustrated, each load plate 450 therefore overlies a respective activeregion of liquid-cooled cold plate 110. As with platens 440, first slipfit regions 451 in load plate 450 slip fit about correspondingregistration pins 420 on one side of the base plate, and second slip fitregions 452 in each load plate 450 slip fit (for instance, by rotatingthe load plate in position) about a respective registration pin 420 onthe other side of the base plate. As illustrated, each registration pinhead 422 overlies a portion of the respective load plate 450, and servesas a stop against which the load plate rests when load pins 455 aretorqued to apply a load to the respective fixture stack segment 500. Aswith platens 440, a further opening or recess 454 may be provided in atleast the end positioned load plates 450 to wrap around the respectiveraised inlet and outlet couplings of liquid-cooled cold plate 110. Notein this regard that the load plates being identically configured, aswell as the load plates being identically configured to the platens areprovided herein by way of example only.

FIG. 7 depicts the assembly of FIG. 6 with the load pins 455 (forinstance, load screws) being torqued, in one or more implementations, aset amount in order to apply a uniform force ‘F’ in a downward directiononto the respective fixture stack segment 500 aligned to a respectiveactive region of the liquid-cooled cold plate 110. The resultant uniformforce is selected to provide a good metallurgical bonding of the heattransfer elements within the active regions of the liquid-cooled coldplate 110 to the base section or shell of the cold plate during heattreatment in, for instance, a braze furnace.

By way of further explanation, FIGS. 8A & 8B depict one embodiment of aprocess for fabricating a liquid-cooled cold plate using a fixture suchas described herein above. As shown, the fixture-based, cold plateassembly process 800 may include placing a pinned registration plate ona workstation surface 802, and placing the base plate of the fixtureonto the pinned registration plate 804. Carbon blocks are placed on thebase plate and positioned to align to the active regions of the coldplate to be fabricated 806. The base shell or section of the cold plateis then placed on the carbon blocks, locating the base section withinthe registration pins 808. A sheet of joining material, such as a sheetof braze or solder material, sized to the outline of each heat transferelement (e.g., finsink) for each cold plate active region is placed ontothe lower section of the cold plate 810. The heat transfer elements(e.g., finsinks) are then placed on the joining material sheets, andaligned with the sheets 812. Appropriately sized sheets of a secondjoining material may be placed on top of each of the heat transferelements 814. By way of specific example, the first joining material maybe a braze material, such as BAg8, and the second joining material maybe a second braze material, such as BCuP5. Alternatively, other joiningmaterials could be used, and note that, in one or more implementations,the first and second joining materials may be the same material. Also, apre-formed braze wire may be placed around the perimeter of the lowersection (or shell) where the upper section (or shell) of the cold plateis to be brazed to the lower section 816. The upper section of theflexible cold plate is then placed onto the assembly, aligning to thelower section of the cold plate. Carbon blocks may be placed on top ofthe upper section of the cold plate over each active region of the coldplate 820. A respective platen may then slid in place over each of theactive regions by slip fitting the platen around respective registrationpins of the registration plate 822.

Continuing with FIG. 8B, a respective load plate is slid in place on topof each of the platens 824. For each load plate, lubricant, such asisopropyl alcohol (IPA) may be applied to the exposed threads of theload pin just above the load plate 826. Before the lubricant evaporates,the load pin may be torqued to a desired torque 828. Note that thecorrect torque should hold the flexible cold plate assembly in positionwith sufficient force to minimize joining or brazing voids, particularlybetween the lower section and the respective heat transfer element(e.g., finsink). When the load plate pins have been torqued in place,the fixture is ready to be removed from the pin registration plate, andplaced in a furnace 830. At the furnace, the inlet/outlet couplings maybe positioned in place on top of the upper section of the cold plate832. The inlet/outlet couplings may have pre-formed braze or solder wireattached to their base to braze or solder the respective coupling to theupper section. In one or more implementations, carbon circles or ringsmay be placed onto the tops of the raised inlet/outlet couplings 834,and an alignment outrigger may be positioned on top of the carboncircles to prevent the raised inlet/outlet couplings from moving duringthe braze or solder process 836. The fixture and cold plate assembly isthen run through the furnace at an appropriate temperature 838. Notethat the furnace employed could be any type of furnace, for instance, abelt furnace, or a vacuum furnace. After the fixture and cold plateassembly have undergone brazing, and cooled so that the fixture can behandled, fixture disassembly may be performed at one time, for instance,in a reverse order of the assembly process 840.

Those skilled in the art will note from the description provided hereinthat numerous advantages are provided by the fixture and fabricationprocess set forth. For instance, the fixture and heat sink (or coldplate) to be fabricated may be assembled quickly, for example, in amatter of seconds, using components that slip fit in place. Inparticular, slip on and slip off platens and load plates are provided.The platens and the load plates include anti-bind features or slip fitregions that allow the platens and load plates to be readily slipped inplace. A uniform load is applied by using a single load pin or screw perload plate, and thus per fixture stack segment (i.e., per active regionof the flexible cold plate). No torque sequencing is required in that asingle screw applies the desired force or load to each segment. Ifdesired, lubricant can be added to the load pin to prevent galling. Byway of example, isopropyl alcohol lubricant could be used, whichevaporates shortly after application. Alternatively, stearic acid,decarboxylates, between 248-290° C., with a peak braze temperature, inone or more embodiments, of 820° C. In particular:CH₃(CH₂)₁₆COOH=>CO₂+CH₃(CH₂)₁₅CH₃

As a further enhancement, the cross-heads or the load pins may be madeof Molybdenum to prevent galling. The single point center loadingapproach disclosed herein provides significant advantages in terms ofuniformity of the resultant metal joined interface across which heat istransferred from, for instance, the respective electronic component tothe heat transfer element of the heat sink.

To summarize, disclosed herein, in one or more implementations, is afixture to facilitate fabrication of a heat sink which includes a lowersection and at least one heat transfer element. The fixture includes abase plate to support the lower section of the heat sink, and multipleregistration pins extending from (e.g., protruding through) the baseplate. Further, the fixture includes at least one platen to reside abovethe at least one heat transfer element of the heat sink, and a platen ofthe at least one platen includes slip fit regions configured to slip fitaround respective registration pins of the multiple registration pinswith the lower section and a respective heat transfer element disposedbetween the base plate and the platen, and forming a fixture stacksegment aligned with an active region of the heat sink to cool aheat-generating electronic component. The fixture also includes at leastone load plate. A load plate of the at least one load plate includesslip fit regions configured to slip fit around correspondingregistration pins of the multiple registration pins with the load platedisposed over the fixture stack segment, above the platen of the atleast one platen, and the load plate including a single load pin. Thesingle load pin is disposed, for instance, centrally in the load plateto contact the platen and facilitate applying a load to the fixturestack segment to assisting bonding (e.g., metallurgically bonding,brazing, soldering, etc.) the respective heat transfer element and thelower section of the heat sink together.

In one or more embodiments, a first slip fit region and a second slipfit region of the slip fit regions in the platen of the at least oneplaten are differently configured to facilitate slip fitting the platenabout the respective registration pins of the multiple registrationpins. Further, in one or more implementations, a first slip fit regionand a second slip fit region of the slip fit regions in the load plateof the at least one load plate are differently configured to facilitateslip fitting the load plate around the corresponding registration pinsof the multiple registration pins.

In one or more embodiments, the platen of the at least one platen, andthe load plate of the at least one load plate, are identicallyconfigured, and for instance, the platen and the load plate slip fitaround the same registration pins of the multiple registration pins. Incertain embodiments, the single load pin is a single load screw which istightened or torqued to apply the load to the platen, and hence to therespective fixture stack segment aligned with the active region of theheat sink.

In one or more implementations, the heat sink includes multiple heattransfer elements, the at least one heat transfer element being at leastone heat transfer element of the multiple heat transfer elements, andthe lower section of the heat sink is a lower shell of the heat sink.The heat sink may also include an upper shell, and the at least one heattransfer element is to be brazed or soldered to the lower shell and tothe upper shell. In one or more embodiments, the heat transfer elementincludes a finsink through which liquid coolant is to flow, and the loadapplied to the fixture stack segment facilitates brazing or solderingthe finsink to the lower shell of the active region of the finsink. Theload applied to the fixture stack segment may further facilitate brazingor soldering the finsink to the upper shell in the active region of theheat sink. In one or more implementations, the heat sink furtherincludes a raised coolant inlet coupling extending from the upper shell,and a raised coolant outlet coupling extending from the upper shell, andthe fixture further includes an alignment outrigger coupled to theraised coolant inlet and outlet couplings to facilitate holding theraised coolant inlet and outlet couplings in position during thermaltreatment of the heat sink.

Further, in one or more implementations, a fixture facilitatesfabrication of a cold plate with multiple heat transfer elements isprovided herein. The fixture includes a base plate to support a lowersection of the cold plate, the cold plate including multiple activeregions, with each active region including a respective heat transferelement to facilitate cooling a respective heat generating electroniccomponent. The fixture also includes multiple registration pinsextending out relative to the base plate, and multiple platens to resideabove an upper section of the cold plate. A platen of the multipleplatens includes slip fit regions configured to slip fit aroundrespective registration pins of the multiple registration pins with thelower section and the upper section of the cold plate disposed betweenthe base plate and the platen, and forming a fixture stack segmentaligned with a heat transfer element in a respective active region ofthe multiple active regions of the cold plate. Further, the fixtureincludes multiple load plates. A load plate of the multiple load platesincludes slip fit regions configured to slip fit around correspondingregistration pins of the multiple registration pins with the load platedisposed over the fixture stack segment, above the platen of themultiple platens, and the load plate includes a single load pin. Thesingle load pin of the load plate may be centrally disposed in the loadplate to facilitate applying a load to the fixture stack segment tofacilitate bonding the lower section, the respective heat transferelement, and the upper section of the cold plate together.

In one or more implementations, the fixture facilitates uniformlybrazing or soldering the multiple heat transfer elements to the lowersection in the multiple active regions thereof. In one or moreembodiments, the multiple heat transfer elements may include multiplefinsinks, with each finsink to be brazed or soldered to the lowersection in a respective active region of the cold plate. In certainembodiments, the slip fit regions in the platen of the multiple platensmay be differently configured to facilitate slip fitting the platenaround the respective registration pins of the multiple registrationpins. Similarly, the slip fit regions in the load plate of the multipleload plates may be differently configured to facilitate slip fitting theload plate around the corresponding registration pins of the multipleregistration pins. In one or more implementations, the registration pinsaround which the load plate is slip fit may include registration pinheads against which the load plate rests when the single load pin isapplying the load to the fixture stack segment.

In one or more further embodiments, a method of facilitating fabricationof a heat sink comprising a lower section and at least one heat transferelement is provided. The method includes providing a fixture, whereproviding the fixture includes: providing a base plate to support thelower section of the heat sink; providing multiple registration pinsextending out from the base plate; providing at least one platen toreside above the at least one heat transfer element of the heat sink, aplaten of the at least one platen including slip fit regions configuredto slip fit around respective registration pins of the multipleregistration pins with the lower section and a respective heat transferelement of the at least one heat transfer element of the heat sinkdisposed between the base plate and the platen, and forming a fixturestack segment aligned with an active region of the heat sink to cool aheat-generating electronic component; and providing at least one loadplate, a load plate of the at least one load plate including slip fitregions configured to slip fit around corresponding registration pinswith the load plate disposed over the fixture stack segment, above theplaten of the at least one platen and the load plate including a singleload pin, the single load pin being disposed in the load plate tocontact the platen and facilitate applying a load to the fixture stacksegment to facilitate bonding the respective heat transfer element andthe lower section of the heat sink together.

In one or more embodiments, the heat sink is a cold plate, which furtherincludes an upper section. Also, the method may further include usingthe fixture to facilitate fabricating the cold plate. The using mayinclude: placing the lower section of the cold plate onto the baseplate, locating the lower section relative to the multiple registrationpins; placing the respective heat transfer element on the lower sectionin the active region of the cold plate configured for cooling therespective heat-generating electronic component, with a braze or soldermaterial disposed between the heat transfer element and the lowersection; placing the upper section of the cold plate onto the lowersection with the heat transfer element in the active region disposedbetween the lower and upper sections; placing the platen of the at leastone platen around the respective registration pins to form the fixturestack segment; placing the load plate of the at least one load platearound the corresponding registration pins of the multiple registrationpins over the fixture stack segment, and above the platen of the atleast one platen; and applying a torque to the single load pin in theload plate to apply the load to the fixture stack segment to facilitatebrazing or soldering of the cold plate, including brazing or solderingof the lower section and the heat transfer element together via thebraze or solder material therebetween.

In a further aspect, the braze or solder material is a first joiningmaterial, and the method further includes providing a second joiningmaterial between the heat transfer element and the upper section of thecold plate in the active region of the cold plate, and between the uppersection and the lower section to facilitate bonding the heat transferelement to the upper section, and facilitate bonding the upper and lowersection together simultaneous with bonding of the heat transfer elementto the lower section. In one or more embodiments, the first joiningmaterial and the second joining material are different braze materials.Further, in one or more embodiments, the heat transfer element may be afinsink. Additionally, in one or more implementations, the method mayinclude applying a lubricant to the load pin prior to the applying ofthe torque, the lubricant comprising isopropyl alcohol or stearic acid.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise” (andany form of comprise, such as “comprises” and “comprising”), “have” (andany form of have, such as “has” and “having”), “include” (and any formof include, such as “includes” and “including”), and “contain” (and anyform contain, such as “contains” and “containing”) are open-endedlinking verbs. As a result, a method or device that “comprises”, “has”,“includes” or “contains” one or more steps or elements possesses thoseone or more steps or elements, but is not limited to possessing onlythose one or more steps or elements. Likewise, a step of a method or anelement of a device that “comprises”, “has”, “includes” or “contains”one or more features possesses those one or more features, but is notlimited to possessing only those one or more features. Furthermore, adevice or structure that is configured in a certain way is configured inat least that way, but may also be configured in ways that are notlisted.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of the present invention has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the invention in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.

What is claimed is:
 1. A fixture to facilitate fabrication of a coldplate with multiple heat transfer elements, the fixture comprising: abase plate to support a lower section of the cold plate, the cold platecomprising multiple active regions, each active region including arespective heat transfer element to facilitate cooling a respectiveheat-generating electronic component; multiple registration pinsextending from the base plate; multiple platens to reside above an uppersection of the cold plate, a platen of the multiple platens includingouter perimeter recesses that define perimeter slip fit regions whichfacilitate slip fit of the platen around respective registration pins ofthe multiple registration pins with the respective registration pinspassing through the outer perimeter recesses in the platen and the lowersection and upper section of the cold plate disposed between the baseplate and the platen, and forming a fixture stack segment aligned with aheat transfer element in a respective active region of the multipleactive regions of the cold plate; and multiple load plates, a load plateof the multiple load plates including outer perimeter recesses thatdefine perimeter slip fit regions which facilitate slip fit of the loadplate around corresponding registration pins of the multipleregistration pins with the corresponding registration pins passingthrough the outer perimeter recesses in the load plate and the loadplate disposed over the fixture stack segment, above the platen of themultiple platens, and the load plate including a single load pin, thesingle load pin of the load plate extending through the load plate andpressing against the platen to facilitate applying a load to the fixturestack segment to facilitate bonding the lower section, the respectiveheat transfer element and upper section of the cold plate together. 2.The fixture of claim 1, wherein the fixture facilitates applying auniform load to the fixture stack segment to facilitate brazing orsoldering the multiple heat transfer elements to the lower section inthe multiple active regions thereof.
 3. The fixture of claim 2, whereinthe multiple heat transfer elements comprise multiple cooling structuresthrough which liquid coolant is to flow, each cooling structure to bebrazed or soldered to the lower section in a respective active region ofthe cold plate.
 4. The fixture of claim 1, wherein the slip fit regionsin the platen of the multiple platens are differently-shaped outerperimeter recesses in the platen to facilitate slip fitting the platenaround the respective registration pins of the multiple registrationpins.
 5. The fixture of claim 1, wherein the slip fit regions in theload plate of the multiple load plates are differently-shaped outerperimeter recesses in the load platen to facilitate slip fitting theload plate around the corresponding registration pins of the multipleregistration pins.
 6. The fixture of claim 1, wherein the correspondingregistration pins around which the load plate is slip fit includeregistration pin heads against which the load plate rests when thesingle load pin is applying the load to the fixture stack segment. 7.The fixture of claim 1, wherein the platen of the multiple platens andthe load plate of the multiple load plates are identically configured,and wherein the platen and the load plate slip fit around the sameregistration pins of the multiple registration pins.
 8. The fixture ofclaim 1, wherein the single load pin is a single load screw disposedcentrally in the load plate.
 9. The fixture of claim 1, wherein therespective heat transfer element comprises a cooling structure throughwhich liquid coolant is to flow.
 10. The fixture of claim 9, wherein theheat sink further comprises a raised coolant inlet coupling extendingfrom the upper shell and a raised coolant outlet coupling extending fromthe upper shell, and wherein the fixture further comprises an alignmentoutrigger coupled to the raised coolant inlet and outlet couplings tofacilitate holding the raised coolant inlet and outlet couplings inposition during thermal treatment of the heat sink.
 11. A method offacilitating fabrication of a cold plate with multiple heat transferelements, the method comprising: assembling a fixture comprising:providing a base plate to support a lower section of the cold plate, thecold plate comprising multiple active regions, each active regionincluding a respective heat transfer element to facilitate cooling arespective heat-generating electronic component; positioning multipleregistration pins to extend from the base plate; slip fitting multipleplatens above an upper section of the cold plate, a platen of themultiple platens including outer perimeter recesses that defineperimeter slip fit regions which facilitate slip fit of the platenaround respective registration pins of the multiple registration pins,with the respective registration pins passing through the outerperimeter recesses in the platen and the lower section and the uppersection of the cold plate disposed between the base plate and theplaten, and forming a fixture stack aligned with a heat transfer elementin a respective active region of the multiple active regions of the coldplate; and slip fitting multiple load plates, a load plate of themultiple load plates including outer perimeter recesses that defineperimeter slip fit regions which facilitate flip fit of the load platearound corresponding registration pins of the multiple registrationpins, with the corresponding registration pins passing through the outerperimeter recesses in the load plate and the load plate disposed overthe fixture stack segment, above the platen of the multiple platens, andthe load plate including a single load pin, the single load pin of theload plate extending through the load plate pressing against the platento facilitate applying a load to the fixture stack segment to facilitatebonding the lower section, the respective heat transfer element and theupper section of the cold plate together.
 12. The method of claim 11,wherein the cold plate further comprises an upper section, and whereinthe method comprises using the fixture to facilitate fabricating thecold plate, the using comprising: placing the lower section of the coldplate onto the base plate, locating the lower section relative to themultiple registration pins; placing the respective heat transfer elementon the lower section of the active region of the cold plate configuredfor cooling the respective heat-generating electronic component, with abraze or solder material disposed between the heat transfer element andthe lower section; placing the upper section of the cold plate onto thelower section of the heat transfer element in the active region disposedbetween the lower plate and the upper sections; slip fitting the platenof the multiple platens around the respective registration pins to formthe fixture stack segment; slip fitting the load plate of the multipleload plates around the corresponding registration pins of the multipleregistration pins over the fixture stack segment, and above the platenof the multiple platens; and applying a torque to the single load pin inthe load plate to apply the load to the fixture stack segment tofacilitate brazing or soldering of the cold plate, including brazing orsoldering of the lower section and the heat transfer element togetherusing the braze or solder material disposed therebetween.
 13. The methodof claim 12, wherein the braze or solder material is a first joiningmaterial, and wherein the method further comprises providing a secondjoining material between the heat transfer element and the upper sectionof the cold plate in the active region of the cold plate, and betweenthe upper section and the lower section to facilitate bonding the heattransfer element to the upper section, and facilitate bonding the upperand lower sections together simultaneously with bonding of the heattransfer element to the lower section.
 14. The method of claim 13,wherein the first joining material and the second joining material aredifferent braze materials.
 15. The method of claim 13, wherein the heattransfer element comprises a cooling structure through which liquidcoolant is to flow, the cooling structure including a plurality of fins.16. The method of claim 15, further comprising applying a lubricant tothe load pin prior to applying the torque, the lubricant comprisingisopropyl alcohol or stearic acid.